Any video on YouTube that has captions can be used, although you'll (probably) have to find a way to avoid auto-generated captions.

For example, from MIT (with friendly CC license). You can use open source tool [GoogleSRT][1] or similar to download captions from YouTube.

See [here][2] for more details.

[![enter image description here][3]][3]


  [1]: http://google2srt.sourceforge.net/en/download.html
  [2]: https://opendata.stackexchange.com/a/4005/1511
  [3]: https://i.sstatic.net/OtYdZ.png